Electrical device



Nov. 5, 1946. v. r. ZELOV 2,410,618

ELECTRICAL DEVICE Filed Oct; 6, 1942 FTQ; 9.

WITNESSES: INVENTOR I f4 as VICTOR I. Z |.ov.

Patented Nov. 5, 1946 UNITED PATENT OFFICE 1 ELEQTRICAL'DEWCE Victor- I. Zelbv, Ro's'emontQP-a. Application October .16, 1942, Serial No. 4611,943

6 Claims. 1

This invention relates to electric plugs and contact elements therefor, more particularly to plugs of the type having two or more contact elements, and has for an object'to provide improved'articles of "this character.

In plugs of this type thecontact elements are usually surrounded by-a molded block of suitable insulating material, for example, Bakelite. In order to obtain this structure, it has been customary to place the contact elements in a hollow mold or cavity and have them molded "into insulating compound by compression, transfer ,o'rinjection methods.

Such an operation is relatively slow, unreliable and expensive, due in part to the necessity of manually placing a set of contact elements in the mold prior to each molding operation, and the difiiculty of maintaining proper positioning of the contact elements during molding or introduction of the plastic material into themold. Where female contacts have been molded into the insulating block, there could be no flexibility to take care of slight axial misalignments of themating male and female contact elements.

It is an object of the present invention to .provide a structure of this charactersuch that the insulating block can be molded separately by conventional r automaticmoldingmethods,

Another object of the invention is to provide a structure wherein, 'shoulda contact element be defective, that element may be replaced without injury to the rest of the-structure. v

Yet, another object of the invention is to progvide an insulating blockhavingopenlngs'molded therein for the reception of contact elements, the openings being of such shape and'so disposed in the block as to secure maximum strength of the latter.

A further object of the inventionls to provide, for use with such a block, a novel contact element insert.

These and other objects are efiected by the invention as will be apparent from the following description and claims, taken in accordancewi'th the accompanying drawing forming a part of this application, in which:

Fig. 1 is a longitudinal sectional view of an electric plug embodying features of the invention, and taken'along'the line II 'of Fig. 2, looking in thedirection indicated bythe arrows;

Fig. 2 is an elevational view of the right-hand end of the structure shown in Fig. 1;

Fig. '3 is an elevational view of the innergnr r left-hand end of the insulator block Ish'oWn 1in "2 Fig. v1 prior to deformation of the protruding ends of the contact element inserts;

Fig. '4 is :a transverse sectional view, taken along the'line 'IVIV of Fig. .1, looking in thedirec'tion indicated by the arrows;

Fig. '5 is =aplan view'of one of the contactelement inserts in an intermediate stage ofman'ufacture;

Fig, 6 is a sectional view, taken along the line V'IVI of Fig.5, looking ln the direction indicated b the arrows;

f'Fi'g, 7 is a sectional view/taken along the line VII-VII of Fig. 6, looking in the dire'ction'in'dicated 'by'the arrows;

Fig. "8 is 'a'nfelevational view of a contact element insert in its completed form;

"Fig. "9 isa View similar to "that 'Of FigfB, but with the contact element rotated degrees about its longitudinal axis; and,

Figs. '10 and 11 are elevatidnal and sectional views, respectively, of the protruding inner ends of the contact elements 'afterexpansio'n against the'inner. end of the'insulatjor block.

Referring now to the drawing more in detail, there is shown at I!) (Fig. '1'), an electric plug comprising an outer cylindrical metallic casing H, closed at one endby the wall l2, the latter having the usual central opening thereth'rough (not shown) "for passageofielectric wires to the interior of the casing, the bpeningbingproVided with the customary bushi'ngfilB and associated iretainingnu't ll 4 and Washer ,l 5. r

A molded icy'lindrical "insulator block IT, canstruct'ed'offsuitable electrical insulating material, for example,l3al 'elite; is positioned within the casing H. The insulator 'block is .Inaterlally shorter than the casing and has "its outer and substantially flush with the corresponding end of the casing, with the result'tha't a space I8 is provided between the inner end. ofthe block and the end Wall [216i the casing.

"The block "H has molded therein .a plurality of openings 19 extending axially therethrough from .end "to end, and in "the construction herein illustrated they are disposed concentrically with end 'of the block.

Each opening T9 houses a metallic insert 25 providing a female contact element, .and each s'uchinse'rt "is formed from a single strip 26 [of sheet metal, ,OrsimiIar "material, folded 1,80 ,de-

grees upon itself.;-a1t'its'midpoint-atlfl. The oven lying end portions 28 of the folded strip are oppositely concaved about the longitudinal axis of the folded strip to provide a sleeve-like female contact element 29, adapted to receive a mating male contact element of an electric device complementary to the electric plug ID.

The sleeve-like contact element 29 may be either elliptical in cross-section or circular; if elliptical, then spaces 3| may be providedbetween the element and the surrounding wall of the cylindrical portion 2| of the opening l9. Such spaces 3| provide resilienc in the contact elements, resulting not only in frictional engagement of the male element by the female element, but also in the provision of desirable flexibility to take care of slight axial misalignment of the mating elements. l

The intermediate portions of the folded strip.

28 are oppositely concaved at 32 about anaxis parallel to the bend 21, to provide a bore 33 extending transversely of the contact insert. While this bore 33 is necessary in only one insert of each plug, as will be hereinafter more fully explained, it may be preferred to form all inserts in the same manner for uniformity of design, resulting in minimum cost of manufacture.

The inserts are of such length that when as sembled in the openings IS, the folded and hattened end 34 projects beyond the inner end of the block into the space la. The fold 21 has its central portion cut away, or notched, at 35, preferably by the provision of opening 31 in the strip 26 before the latter is bent. ,This notch 36 provides for a relatively simple operation to expand the projecting end 34 by the insertion of a pointed tool into the notch to spread the sides thereof, with the results indicated in Figs. 10 and 11, where there is shown formed a cup 38, into which the end of an electric wire may be conveniently soldered, or otherwise secured. The crack 39 at the bottom of the cup will permit escape of gases forming during soldering, but is not suificiently wide for escape of the soldering material itself.

The transverse bore 33 of one of the contact inserts is internally threaded for reception of a screw 4|, extending through aligned openings 42 and 43 in the casing and block, respectively, the opening 43 in the block preferably extending inwardlybeyond the opening Is, as at 44, to provide clearance for the inner end of the screw 4|. This screw serves both to retain the block I! in fixed relation with respect to the casing II, and to Provide a ground from the one contact insert to the. metallic casing, as is frequently required.

Inthe above connection, particular attention I is directed to the angular disposition of the slotlike portions 22 of the openings IS with respect to the periphery of the insulator block. The opening with which the screw 4| is associated has the major axis of its slot-like portion extending radially of the block, while the remaining openings are disposed with minor axes of their slotllke openings extending radially. openings are disposed in this manner in order that as much insulating material as possible be left between the contact and the metallic casing to prevent short-circuiting or grounding and at the same time to avoid undue weakening of the block such as would result if the openings were close to the periphery of the block.

The opening having the grounded contact, insert is disposed as shown in order to provide a threaded bore of greater length than would be attainable otherwise. cuiting or grounding of this contact insert with The latter.

The possibility of short-cirrespect to the metallic casing, due to the closeness of the two parts, is immaterial, as this insert is intentionally grounded by the screw 4|.

The detent 50, mounted on the leaf spring 5|, is provided to temporarily lock the plug ID to a complementary electric member which would have a mating opening for reception of the detent 50, The knob 52 provides means whereby the detent may be manually depressed when it is desired to release the plug. As best shown in Figs. 1 and 3, the block I1 is slotted at 53 for reception of the leaf spring 5|. The spring-pressed detent construction just described forms, in and of itself, no part of the present invention, and no claim is made thereto, per se. The opening 55 provided in the block I1 is conventional and serves to receive a mating guide or polarity pin.

An" important advantage of the construction of contact insert disclosed is the saving in metal over that required for the turned type of insert.

Another advantage lies in the fact that the insert may be made from preplated material, thereby avoiding the necessity of plating the individual inserts. This is frequently of considerable importance, as plating with silver, cadmium or tin is required for many uses of the plug.

Yet another advantage results from the fact that the insert is relatively loose in the opening, with the result that when it is heated incident to soldering a wire to the terminal thereof, it can expand without setting up stresses in the surrounding insulating material which would cause cracking or splitting of the latter, as would ocour With the insert molded into the insulator block.

While this invention has been disclosed in but one form, it will be apparent to those skilled in the art that it is not so limited but is susceptible of modification, and it is desired that the invention be limited only insofar as is required by the prior art or as specifically set forth in therappended claims.

What is claimed is:

1. In an article of the character described, a tubular metallic casing; an insulator block within the casing and having a plurality of openings extending axially therethrough and spaced equidistant radially from the longitudinal axis thereof, saidiopenings being of generally rectangular cross-section throughout a portion of their length and said rectangular cross-sections having major and minor axes, one of said openings having its rectangular portion disposed with its major axisextending radially of the insulator block and the remaining openings having their rectangular portions disposed with their minor axes extending radially of the block; metallic contact elements in said openings and including rectangular portions in the rectangular portions of the openings; and a metallic member providing an electrical connection between the rectangular portion of the contact element in said one opening and the metallic casing, whereby an electrical ground is provided between said casing and the nearest of said contact elements.

2. In an article of the character described, a tubular metallic casing; an insulator block within the casing and having a plurality of openings extending axially therethrough and spaced equidistant radially from the longitudinal axis thereof; metallic contact elements in said openings, each of said elements being of non-circular cross-section throughout a portion of its length and said non-circular cross-section having major .5 and minor axes; and a metallic member providing an electrical ground between the metallic casing and the non-circular portion of one of the metallic contact elements, said one contact element being disposed with the major axis of its noncircular portion extending radially of the block and casing to provide minimum grounding distance between said contact element and the casing, and the remaining contact elements being disposed with the minor axes of their non-circular portions extending radially of the block and casing to provide maximum insulation thickness between said remaining contact elements and the casing.

3. In an article of the character described, a tubular metallic casing open at one end and partially closed at the other end; an insulator block within the casing with its inner end spaced a material distance from the closed end of the casing, said block having a plurality of openings therethrough from end to end, said openings being of generally rectangular cross-section adjacent the inner end of the block and said crosssections having major and minor axes, one of said openings having its rectangular portion disposed with its major axis extending radially of the insulator block and the remaining openings having their rectangular portions disposed with their minor axes extending radially of the block; metallic contact elements in said openings, said elements including first female portions, second fiat portions fitting the rectangular portions of the openings, and third expanded portions extending into the space between the closed end of the casing and the inner end of the block, said third portions being adapted to have electrical conductors connected thereto, the contact element in said one opening having an opening through its rectangular portion, the axis of said last-mentioned opening extending radially of the block; and a metallic member having one end secured in said last-mentioned opening and its other end in contact with the casing.

4. In an article of the character described, a cylindrical casing closed at one end; a cylindrical insulator block of lesser length than said casing positioned within the latter with its inner end spaced from the closed end of the casing, said block having a plurality of openings extending axially therethrough and said openings being of reduced cross-sectional area near their inner ends; and metallic inserts in said openings, the outer portions of said inserts providing female contact elements and the inner portions of said inserts extending through the reduced portions of the openings and being deformed therebeyond to anchor the inserts in the openings, the deformed inner ends of the inserts providing cupped terminals into which the ends of electrical wires may be soldered or similarly secured, said cupped 6 terminals having slits or cracks in the bottom portions thereof through which gasses, formed during soldering or similar securing operations, may escape.

5. An electrical plug comprising a tubular metallic casing; an insulator block within said casing and having a plurality of openings extending axially therethrough and spaced concentrically about the longitudinal axis thereof, said openings being slot-like in cross-section adjacent one end of the block, the slot of one of said openings extending radially of the block and the slots of the remaining openings extending normal to radii of the block; a metallic insert in each of said openings and extending beyond said one end of the block for the attachment thereto of electrical conductors, the other end of each insert comprising a female contact element, and the insert in said one opening having means providing an internally-threaded bore disposed radially of the block; and a metallic member threaded into said bore and extending through the adjacent side wall of the block and contacting the metallic casing.

6. In an article of the character described, a cylindrical metallic casing closed at one end; a cylindrical insulator block of lesser length than said casing positioned within the latter with its inner end spaced from the closed end of the casing, said block having a plurality of openings extending axially therethrough, said openings being generally cylindrical from the outer end of the block for a portion of their length and being of reduced cross-section for the remainder of their length to the inner end of the block, said reduced cross-section being rectangular with major and minor axes, one of said openings bein disposed with the major axis of its rectangular cross-section extending radially of the block and the remaining openings being disposed with the minor axes of their rectangular cross-sections extending radially of the block; metallic inserts in said openings, the portions of said inserts which occupy the cylindrical portions of the openings providingfemale contact elements and the remaining portions having parts of rectangular crosssection fittin the correspondingly shaped portions of the openings, the ends of said inserts extending beyond the inner end of the insulator block into the space between said inner end and the closed end of the casing and providing terminals to which wires may be attached, the insert in said one opening having an internallythreaded opening therein extending radially of the block; and a screw extending through aligned openings in said casing and block and threadedly received in said internally-threaded opening and providin an electrical ground from said metallic insert to the metallic casing.

VICTOR I. ZELOV. 

